Sr and Nd isotopic evidence for punctuated clay diagenesis, Texas Gulf Coast

We report Rb---Sr, Sm---Nd and mineralogical data for leached whole rock, 87Sr/86Sr from 0.708 to 0.711 in exchangeable sites. Leached authigenic illite from the 1200 m, independent of the duration of burial. The exchangeable Sr in the clay has remained an open system and has undergone isotopic exchange since that time. Minimum fluid/rock ratios of 0.2 to 2 are modeled from Sr isotopic data, consistent with rock-dominated, open system diagenesis. Leachates and residues of the 147Sm/144Nd ( 147Sm/144Nd as high as 0.188. This Sm/Nd fractionation, in conjunction with the preserved isotopic equilibrium may be useful for dating diagenesis and associated fluid-rock interaction in older rocks.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/29242/1/0000298.pd

Mobility and fractionation of rare earth elements in argillaceous sediments: Implications for dating diagenesis and low-grade metamorphism

We report Sm-Nd and Rb-Sr data for the fine fractions of Lower Paleozoic argillaceous rocks from Wales, UK and New York, USA, spanning the range of low-grade metamorphic conditions from the diagenetic zone (zeolite facies) to the epizone (greenschist facies). In all cases, leaching of the fine fractions results in a high 147Sm/144Nd (0.09-0.29) acid-soluble component and a complementary low 147Sm/144Nd (0.05-0.14) residual component. The observed fractionation is an ancient feature related to diagenesis, burial and metamorphism. The magnitude of Sm-Nd fractionation between leachates and residues, as well as the resulting Sm-Nd ages, vary as a function of grain size and metamorphic grade. Uncleaved Welsh mudrocks of the diagenetic zone yield Sm-Nd leachate-residue ages of 453-484 Ma, in agreement with their Llanviian to Caradocian biostratigraphic ages, whereas higher grade rocks of the anchizone and epizone yield Sm-Nd ages as young as 413 Ma. These ages are transitional between the time of deposition and the time of regional deformation related to the Acadian Orogeny at 390 Ma. Distinct convex-upward rare earth element (REE) patterns of the leachates suggest that the precipitation of early diagenetic apatite controls the trace element budget of the rock, forcing a depletion of middle REEs on the subsequently formed diagenetic phyllosilicates. The amount of organic matter present and the extent of later prograde reactions are probable modifiers of this fractionation process. Ordovician and Devonian clastic rocks associated with the Trenton and Onondaga limestones of New York yield single-sample and multi-sample Sm-Nd isochron ages that agree well with their biostratigraphic ages of 454 Ma and 390 Ma, respectively. The REE fractionation observed in shale leachates of the Ordovician Utica Formation is related to Ca/Mg of the bulk rock and hence to the composition of the diagenetic carbonate cement. In all cases the Sm-Nd system remained closed subsequent to the peak of diagenesis or metamorphism, including the North American rocks that show no evidence of being isotopically reset during widespread remagnetization of the subjacent limestone units in the late Paleozoic.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/31915/1/0000868.pd

Explodierende Staatsschulden, drohende Staatsbankrotte: Was kommt auf uns zu?

Seit Ausbruch der Finanz- und Wirtschaftskrise ist weltweit ein enormer Anstieg staatlicher Defizite und Schuldenstände zu beobachten. Was bedeutet die Entwicklung für die Europäische Währungsunion? Charles B. Blankart und Erik R. Fasten, Humboldt-Universität zu Berlin, finden es wünschenswert, »vom Nichtauslösungsartikel auszugehen und diesen mit einem Verfahren wie dem des Eurostabilitätspaktes zu verbinden. Die Mitgliedstaaten sagen Hilfe zur Restrukturierung zu. Aber wenn dies alles nichts fruchtet, so steht am Ende … nicht die Auslösung, sondern der Staatsbankrott«. Jörn Axel Kämmerer und Hans-Bernd Schäfer, Bucerius Law School, Hochschule für Rechtswissenschaft, Hamburg, sehen die Europäische Union vor einem äußerst schmalen Grat. Die EU dürfe das Bail-out-Verbot nicht zum Schaden des Euro in einer Weise aufweichen, dass »die Ausnahme zur Regel« werde. Aber sie könne auch nicht untätig bleiben. Jörg Asmussen, Bundesministerium der Finanzen, unterstreicht, dass sich der Stabilitäts- und Wachstumspakt als fiskalpolitisches Koordinierungsinstrument bewährt habe. Auf der anderen Seite werden jetzt die Regeln wieder restriktiver angewandt. Dies bedeute, dass alle Mitgliedstaaten ihre Haushalts- und/oder Strukturprobleme aus eigener Kraft in den Griff bekommen müssen. Für Christian Tietje, Universität Halle-Wittenberg, bleibt es zunächst immer bei der Selbstverantwortung der Staaten der Eurogruppe für ihre Wirtschaftspolitik, finanzielle Solidaritätsmaßnahmen müssen die Ultima Ratio im Euroraum bleiben. Michael Kühl und Renate Ohr, Universität Göttingen, sind der Meinung, dass hochverschuldete Länder, wie z.B. Griechenland, selbst einen Weg finden müssen, ihre Staatsfinanzen zu konsolidieren.Öffentliche Schulden, Wirtschaftskrise, Haushaltskonsolidierung, Europäische Wirtschafts- und Währungsunion, Staatsbankrott, Finanzpolitik, Deutschland, Griechenland, Italien, Belgien, EU-Staaten

Effects of crack tip geometry on dislocation emission and cleavage: A possible path to enhanced ductility

We present a systematic study of the effect of crack blunting on subsequent crack propagation and dislocation emission. We show that the stress intensity factor required to propagate the crack is increased as the crack is blunted by up to thirteen atomic layers, but only by a relatively modest amount for a crack with a sharp 60$^\circ$ corner. The effect of the blunting is far less than would be expected from a smoothly blunted crack; the sharp corners preserve the stress concentration, reducing the effect of the blunting. However, for some material parameters blunting changes the preferred deformation mode from brittle cleavage to dislocation emission. In such materials, the absorption of preexisting dislocations by the crack tip can cause the crack tip to be locally arrested, causing a significant increase in the microscopic toughness of the crack tip. Continuum plasticity models have shown that even a moderate increase in the microscopic toughness can lead to an increase in the macroscopic fracture toughness of the material by several orders of magnitude. We thus propose an atomic-scale mechanism at the crack tip, that ultimately may lead to a high fracture toughness in some materials where a sharp crack would seem to be able to propagate in a brittle manner. Results for blunt cracks loaded in mode II are also presented.Comment: 12 pages, REVTeX using epsfig.sty. 13 PostScript figures. Final version to appear in Phys. Rev. B. Main changes: Discussion slightly shortened, one figure remove

DARTAB: a program to combine airborne radionuclide environmental exposure data with dosimetric and health effects data to generate tabulations of predicted health impacts

The DARTAB computer code combines radionuclide environmental exposure data with dosimetric and health effects data to generate tabulations of the predicted impact of radioactive airborne effluents. DARTAB is independent of the environmental transport code used to generate the environmental exposure data and the codes used to produce the dosimetric and health effects data. Therefore human dose and risk calculations need not be added to every environmental transport code. Options are included in DARTAB to permit the user to request tabulations by various topics (e.g., cancer site, exposure pathway, etc.) to facilitate characterization of the human health impacts of the effluents. The DARTAB code was written at ORNL for the US Environmental Protection Agency, Office of Radiation Programs

Phase I Study of Ficlatuzumab and Cetuximab in Cetuximab-Resistant, Recurrent/Metastatic Head and Neck Cancer

etuximab, an anti-EGFR monoclonal antibody (mAb), is approved for advanced head and neck squamous cell carcinoma (HNSCC) but benefits a minority. An established tumor-intrinsic resistance mechanism is cross-talk between the EGFR and hepatocyte growth factor (HGF)/cMet pathways. Dual pathway inhibition may overcome cetuximab resistance. This Phase I study evaluated the combination of cetuximab and ficlatuzumab, an anti-HGF mAb, in patients with recurrent/metastatic HNSCC. The primary objective was to establish the recommended Phase II dose (RP2D). Secondary objectives included overall response rate (ORR), progression-free survival (PFS), and overall survival (OS). Mechanistic tumor-intrinsic and immune biomarkers were explored. Thirteen patients enrolled with no dose-limiting toxicities observed at any dose tier. Three evaluable patients were treated at Tier 1 and nine at Tier 2, which was determined to be the RP2D (cetuximab 500 mg/m2 and ficlatuzumab 20 mg/kg every 2 weeks). Median PFS and OS were 5.4 (90% CI = 1.9–11.4) and 8.9 (90% CI = 2.7–15.2) months, respectively, with a confirmed ORR of 2 of 12 (17%; 90% CI = 6–40%). High circulating soluble cMet levels correlated with poor survival. An increase in peripheral T cells, particularly the CD8+ subset, was associated with treatment response whereas progression was associated with expansion of a distinct myeloid population. This well-tolerated combination demonstrated promising activity in cetuximab-resistant, advanced HNSCC